The oxygen mixture was itself not flammable, but it is believed he set fire to the chamber's sheets, which led to the explosion.

Health and safety experts together with firemen who investigated the explosion confirmed they had found a melted lighter inside the chamber.

The man's son who had been visiting his father has demanded to know how the hospital could have failed to take away the man's lighter.

He said: "My father's whole body was scorched, he looked just like a roasted pig.

"It was the worst thing I have ever seen and was absolutely unbearable."

Treatment in a hyperbaric oxygen chamber is believed to help the healing of wounds by helping the red blood cells to carry more oxygen which speeds up the healing process.

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Angry: Dead man's son demands inquiry.

Hospital spokesman Yong Wan said: "Mr Liu had already undergone one treatment which had worked well.

"We assume he had probably decided during the second treatment he would try to sneak a cigarette where he couldn't be seen, as smoking in the hospital was not allowed."

Despite the fact that the cigarette destroyed an expensive piece of equipment the hospital has admitted responsibility in not warning its patient that smoking or taking a lighter into the device could be dangerous.